Experimental: Tryptophan in healthy young adults (18-45 years) for Healthy Subjects

Tryptophan is an essential amino acid needed for growth and bodily functions. It is used to make serotonin which is needed for the brain to develop and function properly. However, when the body is stressed, tryptophan is broken down into compounds that can cause harm to the brain. Premature babies who get nutrition through their vein \[i.e. total parenteral nutrition (TPN)\] can experience this type of stress. The amount of tryptophan in TPN solutions is much higher than what premature babies need and can produce too much harmful compounds. So, it is important to study the amount of these compounds made from tryptophan. But there are no methods available to study this. Therefore, the goal of this study is to develop a method to measure the compounds made from tryptophan breakdown in adults so that it can be used for preterm babies on TPN later.